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Updated: Jun 19, 2026
Screening Foodstuffs for Class 1 Integrons and Gene Cassettes
Published on: June 19, 2015
Detection and characterization of class 1 integrons in Aeromonas spp. isolated from human diarrheic stool in Mexico
Abigail Pérez-Valdespino1, Elizabeth Fernández-Rendón, Everardo Curiel-Quesada
1Department of Biochemistry, Escuela Nacional de Ciencias Biológicas del Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala S/N, Col. Santo Tomás, CP 11340. Mexico City, Mexico.
Abstract:
We determined the presence of class 1 integrons related to the acquisition of resistance to antimicrobials in Aeromonas spp. isolated from individuals with diarrhea. Species were identified as A. caviae, A. hydrophila, A. veronii and A. media using PCR-RFLP of the 16S rDNA. Selected isolates were further characterized by ERIC-PCR. Resistance to chloramphenicol, aztreonam, tetracycline, trimethoprim/sulfamethoxazole, nalidixic acid and streptomycin, among others, was determined using the Kirby-Bauer method. Integrons were detected by PCR amplification of the 5' conserved, variable, and 3' conserved regions. Sequencing of the variable regions revealed class 1 integrons with cassettes encoding resistance to trimethoprim (dfrA12, dfrA15, dfrB4), streptomycin/spectinomycin (aadA2, aadA1), oxacillin (oxa2) and chloramphenicol (catB3, cmlA4). Others had an open reading frame (orfD) or no insert at all. To our knowledge, this is the first description of the occurrence of genes cmlA4 and dfrA15 in Aeromonas class 1 integrons. Not all the integron-linked cassettes conferred their associated resistances, which suggests the inactivity of some cassettes. Most integrons were chromosomally located. The presence of class 1 integrons similar to those found in a wide variety of bacterial genera from different origins, including environmental and fish-borne Aeromonas, confirms the stability and horizontal transfer of these genetic elements.
Insights
Class 1 integrons linked to antimicrobial resistance were found in Aeromonas species from diarrhea patients. This study identifies new resistance genes in these mobile genetic elements, confirming their stability and transferability.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Aeromonas species are opportunistic pathogens causing diarrheal diseases.
- Antimicrobial resistance is a growing global health concern.
- Class 1 integrons are key genetic elements facilitating the spread of antimicrobial resistance.
Purpose of the Study:
- To investigate the presence and characteristics of class 1 integrons in Aeromonas spp. isolated from human diarrheal infections.
- To identify antimicrobial resistance genes associated with these integrons.
- To understand the genetic location and transferability of these elements.
Main Methods:
- Species identification using PCR-RFLP of 16S rDNA.
- Antimicrobial susceptibility testing via Kirby-Bauer method.
- Detection and sequencing of class 1 integrons using PCR and sequencing.
Main Results:
- Class 1 integrons were detected in Aeromonas species (A. caviae, A. hydrophila, A. veronii, A. media).
- Identified resistance genes included dfrA12, dfrA15, dfrB4 (trimethoprim), aadA2, aadA1 (streptomycin/spectinomycin), oxa2 (oxacillin), and catB3, cmlA4 (chloramphenicol).
- Genes cmlA4 and dfrA15 were newly described in Aeromonas class 1 integrons; some cassettes were inactive, and most integrons were chromosomal.
Conclusions:
- Class 1 integrons carrying diverse antimicrobial resistance genes are present in human diarrheal Aeromonas isolates.
- The findings highlight the potential for horizontal gene transfer and the stability of these mobile genetic elements.
- This study contributes to understanding the epidemiology of antimicrobial resistance in Aeromonas species.
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